Auxiliary gravity drain and infiltration wells supporting basic drainage system in the «Bełchatów» Lignite Mine

Abstract

The downhole parts of the «Bełchatów» Lignite Mine are dewatered through large diameter dewatering wells belonging to the primary drainage system. This system is supported by additional shallow wells performed in the overburden, in the forefield of extraction site or on the extraction site itself. They are used for limiting and removing residual water from extraction site, which corresponds to the height of excavator level. They are preceded by the analysis of dewatering of the mining benches based on the results of control drilling and observation of the water table in the existing piezometric wells. Shallow auxiliary wells are drilled with the »dry« rotary method to about 30 m of depth. Such wells considerably reduce the amount of water coming to the mine with rainwaters, and which were not captured by wells of the primary drainage system. This is mainly caused by such factors as complex geological build, disturbed system of strata, presence of synclinal structures and closed lenses. The technique and technology of drilling supporting shallow wells with the »dry« rotary method and their effect on dewatering of active extraction sites are discussed in this paper.